Getting started with a real aquarium

A first aquarium does not have to be difficult. Most problems come from a few common mistakes: a tank that is too small, fish added too soon, or too many fish at once. Avoid those, and you are most of the way there.

Choose the tank

Bigger is easier. A larger volume of water changes more slowly when something goes wrong — a missed feeding, a hot day, a fish that dies unnoticed — so a tank of 60 litres or more is a much better start than a small one. Place it on a stand built for the weight (water weighs a kilo per litre), away from direct sunlight, which feeds algae, and close to a power socket.

The equipment

• A filter sized for the tank. It moves the water, but its most important job is to house the bacteria that break down fish waste.
• A heater with a thermostat for tropical fish; some fish, such as zebra danios, do fine at room temperature.
• A light on a timer, around eight hours a day.
• Substrate — sand or gravel — and plants. Live plants help keep the water clean and give fish places to hide.
• A water conditioner that removes chlorine from tap water, and a simple test kit for ammonia, nitrite and nitrate.

Cycle the tank before adding fish

Fish waste produces ammonia, which is poisonous. In a healthy tank, bacteria turn ammonia into nitrite (also poisonous) and then into nitrate, which is far less harmful and is removed with water changes. This is the nitrogen cycle, and a new tank does not have those bacteria yet.

So set up the tank, run the filter, and "feed" it a small source of ammonia — a pinch of fish food or bottled ammonia — for several weeks, testing as you go. When ammonia and nitrite both read zero a day after feeding, the tank is cycled. It usually takes four to six weeks. Bottled bacteria and filter material from an established tank can speed it up.

Choose your first fish

Add a few fish at a time, a week or two apart, so the bacteria can keep up. Good first fish are hardy and peaceful: guppies, zebra danios, cherry barbs and corydoras. Check how large each fish grows, whether it needs a group, and whether it gets along with the others before you buy. More demanding fish, such as discus, are better left until you have some experience.

The weekly routine

• Feed small amounts once or twice a day — only what the fish eat in a couple of minutes.
• Change about a quarter of the water every week, using conditioned water at the same temperature.
• Rinse the filter material in old tank water when it clogs, never under the tap, which would kill the bacteria.
• Look at your fish every day. A fish that hides, stops eating or clamps its fins is often the first sign that something is wrong.

Once that routine feels easy, you can try live plants, an aquascape, or even a pondarium — see aquarium, pond or aquascape?